Every number, its federal source, and the date we read it

the rule we work by

Three lines that decide what gets published

A number carries its source and its date, or it does not go on the page. Not "according to NOAA" but which dataset, which period, and the day we pulled it. A figure with no date is a figure nobody can check.

Our arithmetic is labelled as ours. When we multiply a federal figure by something, the multiplication is our work and the page says so. A calculation presented as a measurement is the most common dishonesty in this category, and it is usually accidental.

Where two federal sources disagree, we show both and say which one we follow. This happens more than you would expect. The clearest case is on this site: the EPA puts the altitude at which you boil water for three minutes at 5,000 feet, and the CDC puts it at 6,500. We use the lower one, and we say why.

nine calculators, nine sources

What sits behind each tool

Every dataset above is public and free. Where a page uses a figure that is not in this table, that figure carries its own source line on the page itself.

what is ours, not theirs

The arithmetic we do, stated plainly

Federal agencies publish figures. They do not publish answers for your house. The gap between the two is our work, and this is all of it.

• Rain barrel. Roof area multiplied by the USGS per-square-foot figure, then by your state's rainfall. The first-flush loss and the number of rains per month are your estimates, not data, and the page says so.
• Water from air. Grams of water per cubic metre come from the Magnus formula applied to NOAA's dew point and temperature. That is physics, not measurement: it says what the air holds with perfect capture, which no machine achieves. We make no claim about any product's yield.
• Drought map. The only arithmetic is adding the state population figures into a national one. Every percentage is the Drought Monitor's own, and they are cumulative, which the page explains rather than leaving you to add them wrongly.
• Generator or battery. Outage minutes converted to hours. The appliance wattages are our starting estimates and the page tells you to replace them with what is printed on your own equipment.
• 30-day pantry. Prices and calories are federal. What goes on the list, in what proportion, and the four-week buying order are our judgement, and the page says so.
• Water treatment. The published per-gallon dose multiplied by your container size, using the CDC's own equivalence of 8 drops to half a millilitre. No dose here is a recipe of ours. For chlorine dioxide we publish no dose at all, because the federal guidance points at the packet.
• Blackout kit. The survey publishes tank sizes in bands, so we count the bottom of your band. Inventing a midpoint inside a published band would be creating a number the data does not contain. The real figure is that or more.

for extension offices, emergency managers and librarians

Free to cite, free to embed

If you publish guidance on household water, food or power, you are welcome to link or embed any of these tools. There is no charge, no sign-up, no email wall and no advertising inside them. We ask only that the credit line stays visible.

To embed the rain barrel calculator:

<iframe src="https://theselfreliantgarden.com/embed/rain-barrel/"
        width="100%" height="1300" style="border:0" loading="lazy"
        title="Rain barrel calculator, by state"></iframe>

The embedded version carries no navigation, no email capture and no affiliate link. On a narrow screen the form stacks and the frame scrolls; the state table opens on click so it does not dominate the height. If you would like a different tool packaged the same way, ask and we will build it.

To cite us in text: The Self-Reliant Garden, "name of the tool", theselfreliantgarden.com, with the date you read it. The underlying federal dataset is named on every tool page, and citing that directly is equally welcome and often better.

how this is paid for

Where the money comes from, and where it does not

Four pages on this site review a product and carry an affiliate link, which means we may earn a commission if you buy through one. Those four are gathered in Products and each says so next to every button.

The nine calculators and every guide carry none. No affiliate link, no sponsor, no advertising. That is deliberate and it is why they can be embedded on a public agency's page without a conflict. If that ever changes, this paragraph changes with it and the change will be dated.

if we got something wrong

Tell us, and we will date the correction

A number here can be stale, a source can be updated, and we can simply be wrong. Write to us through the contact page. Corrections are made on the page, with the date, rather than quietly.